Routing in packet-switched networks between a source and one or more destinations presents many challenges. Routing issues may be particularly acute in Multiprotocol Label Switching (MPLS) networks which use a Point-to-Multipoint (P2MP) Traffic Engineering (TE) Label Switched Path (LSP) crossing a number of domains, due in part to having to compute a route for each of a number of destinations and due in part to having to compute routes potentially spanning multiple domains.
In some networks, such as MPLS networks, a TE P2MP LSP may be established using a Resource Reservation Protocol-TE (RSVP-TE) for a given path. A path can be computed by a Path Computation Client (PCC) and/or a Path Computation Element (PCE). For example, the PCC may request a path or route from a PCE, which computes the path and sends the computed path information back to the PCC. The path may be a P2MP path from a source node to a plurality of destination nodes, which crosses a plurality of domains, where a domain may be a collection of network elements within a common sphere of address management or path computational responsibility, such as an Interior Gateway Protocol (IGP) area or an Autonomous System.
Previous systems and methods for routing or determining a P2MP LSP may suffer from numerous drawbacks, including that a sequence of domains (sometimes referred to as a core tree of domains) from a source to multiple destinations must be known in advance, and there may be no guarantee that a path crossing multiple domains computed is shortest. The Internet Engineering Task Force (IETF) draft-zhao-pce-pcep-inter-domain-p2 mp-procedures-06 entitled “PCE-based Computation Procedure to Compute Shortest Constrained P2MP Inter-domain Traffic Engineering Label Switched Paths”, which is incorporated herein by reference, describes one procedure that relies on the use of multiple PCEs to compute an MPLS TE P2MP LSP path across a plurality of domains. The procedure suffers from some of the drawbacks discussed above.